SDMA communications with non-immediate block acknowledgment

ABSTRACT

In Spatial Division Multiple Access (SDMA) communications, mobile devices that are transmitting to a base station substantially simultaneously during a predetermined communications phase may wait until after an end of the predetermined communications phase to receive acknowledgments to their transmissions, so that a mobile device making a relatively short transmission does not experience an acknowledgment timeout while another mobile device is still completing a relatively long transmission. In some embodiments, the mobile devices may transmit a non-immediate block acknowledgment request during the communications phase.

BACKGROUND

To address the problem of ever-increasing bandwidth requirements thatare placed on wireless data communications systems, various techniquesare being developed to allow multiple devices to communicate with asingle base station by sharing a single channel. In one such technique,a base station may transmit or receive separate signals to or frommultiple mobile devices at the same time on the same frequency, providedthe mobile devices are located in sufficiently different directions fromthe base station. For transmission from the base station, differentsignals may be simultaneously transmitted from each of separatespaced-apart antennas so that the combined transmissions aredirectional, i.e., the signal intended for each mobile device may berelatively strong in the direction of that mobile device and relativelyweak in other directions. In a similar manner, the base station mayreceive the combined signals from multiple independent mobile devices atthe same time on the same frequency through each of separatespaced-apart antennas, and separate the combined received signals fromthe multiple antennas into the separate signals from each mobile devicethrough appropriate signal processing so that the reception isdirectional.

Under currently developing specifications, such as IEEE 802.11 (IEEE isthe acronym for the Institute of Electrical and Electronic Engineers, 3Park Avenue, 17th floor, New York, N.Y.), each mobile device maytransmit a data block of variable length, and then wait for apredetermined timeout period after the data block for an acknowledgmentfrom the base station to signify that the base station received the datablock. If the base station transmits and receives on the same frequency,that fact may preclude the base station from transmitting and receivingat the same time, so that the base station waits until all incoming datablocks are complete before sending out any acknowledgments. However,since the data blocks are of variable length, a mobile device sending ashort data block may experience an acknowledgment timeout while the basestation is still receiving a long data block from another mobile device.The resulting unnecessary retransmission of the short data block maycause inefficiencies in the overall data communications, and under somecircumstances may even result in a service interruption.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 shows a diagram of a communications network, according to anembodiment of the invention.

FIG. 2 shows a timing diagram of a communications sequence involving abase station and two mobile devices, according to an embodiment of theinvention.

FIG. 3 shows a flow chart of a method that may be performed by a basestation, according to an embodiment of the invention.

FIG. 4 shows a flow chart of a method that may be performed by a mobiledevice, according to an embodiment of the invention.

FIG. 5 shows a block diagram of a base station, according to anembodiment of the invention.

FIG. 6 shows a block diagram of a mobile device, according to anembodiment of the invention.

FIG. 7 shows communications formats that may be used in a communicationssequence, according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description, numerous specific details are set forth.However, it is understood that embodiments of the invention may bepracticed without these specific details. In other instances, well-knownmethods, structures and techniques have not been shown in detail inorder not to obscure an understanding of this description.

References to “one embodiment”, “an embodiment”, “example embodiment”,“various embodiments”, etc., indicate that the embodiment(s) of theinvention so described may include a particular feature, structure, orcharacteristic, but not every embodiment necessarily includes theparticular feature, structure, or characteristic. Further, repeated useof the phrase “in one embodiment” does not necessarily refer to the sameembodiment, although it may.

In the following description and claims, the terms “coupled” and“connected,” along with their derivatives, may be used. It should beunderstood that these terms are not intended as synonyms for each other.Rather, in particular embodiments, “connected” may be used to indicatethat two or more elements are in direct physical or electrical contactwith each other. “Coupled” may mean that two or more elements are eitherin direct physical or electrical contact, or that two or more elementsare not in direct contact with each other but yet still co-operate orinteract with each other.

As used herein, unless otherwise specified the use of the ordinaladjectives “first”, “second”, “third”, etc., to describe a commonobject, merely indicate that different instances of like objects arebeing referred to, and are not intended to imply that the objects sodescribed must be in a given sequence, either temporally, spatially, inranking, or in any other manner.

Unless specifically stated otherwise, as apparent from the followingdiscussions, it is appreciated that throughout the specificationdiscussions utilizing terms such as “processing,” “computing,”“calculating,” or the like, refer to the action and/or processes of acomputer or computing system, or similar electronic computing device,that manipulate and/or transform data represented as physical, such aselectronic, quantities into other data similarly represented as physicalquantities.

In a similar manner, the term “processor” may refer to any device orportion of a device that processes electronic data from registers and/ormemory to transform that electronic data into other electronic data thatmay be stored in registers and/or memory. A “computing platform” maycomprise one or more processors.

In the context of this document, the term “wireless” and its derivativesmay be used to describe circuits, devices, systems, methods, techniques,communications channels, etc., that may communicate data through the useof modulated electromagnetic radiation through a non-solid medium. Theterm does not imply that the associated devices do not contain anywires, although in some embodiments they might not.

In keeping with common industry terminology, the terms “base station”,“access point”, and “AP” may be used interchangeably herein to describean electronic device that may communicate wirelessly and substantiallysimultaneously with multiple other electronic devices, while the terms“mobile device” and “STA” may be used interchangeably to describe any ofthose multiple other electronic devices, which may have the capabilityto be moved and still communicate, though movement is not a requirement.However, the scope of the invention is not limited to devices that arelabeled with those terms. Similarly, the terms “spatial divisionmultiple access” and SDMA may be used interchangeably. As used herein,these terms are intended to encompass any communication technique inwhich different signals may be transmitted by a combination of antennassubstantially simultaneously from the same device such that the combinedtransmitted signals result in different signals intended for differentdevices being transmitted substantially in different directions on thesame frequency, and/or techniques in which different signals may bereceived substantially simultaneously through multiple antennas on thesame frequency from different devices in different directions and thedifferent signals may be separated from each other through suitableprocessing. The term “same frequency”, as used herein, may includeslight variations in the exact frequency due to such things as bandwidthtolerance, Doppler shift adaptations, parameter drift, etc. Two or moretransmissions to different devices are considered substantiallysimultaneous if at least a portion of each transmission to the differentdevices occurs at the same time, but does not imply that the differenttransmissions must start and/or end at the same time, although they may.Similarly, two or more receptions from different devices are consideredsubstantially simultaneous if at least a portion of each reception fromthe different devices occurs at the same time, but does not imply thatthe different transmissions must start and/or end at the same time,although they may. Variations of the words represented by the term SDMAmay sometimes be used by others, such as but not limited to substituting“space” for “spatial”, or “diversity” for “division”. The scope ofvarious embodiments of the invention is intended to encompass suchdifferences in nomenclature.

Some embodiments of the invention may comprise the transmission of adata burst from a mobile device to a base station, in which the databurst includes a request for a non-immediate block acknowledgment fromthe base station. A data burst may comprise one block of data, ormultiple sequential blocks (sub-bursts) of data. A non-immediateacknowledgment may be an acknowledgment that can be delayed until alater time rather than being sent within a predetermined time after theend of the data that is being acknowledged. A block acknowledgment maybe a single acknowledgment that acknowledges multiple sub-bursts ratherthan requiring a separate acknowledgment for each of the multiplesub-bursts. In some embodiments, a block acknowledgment may identifyeach of the sub-bursts that is being acknowledged, so that somesub-bursts may be acknowledged while others are not, even thought asingle block acknowledgment is being used. Thus, a non-immediate blockacknowledgment may acknowledge all or individual ones of a group ofsub-bursts, and may be delayed until an appropriate acknowledgment timewithout causing acknowledgement timeouts for the individual sub-bursts.

FIG. 1 shows a diagram of an SDMA communications network that may usenon-immediate block acknowledgments in SDMA operations, according to anembodiment of the invention. The illustrated embodiment of acommunications network shows an AP 110 that may communicate withmultiple STAs 131-134 located in different directions from the AP. TheAP 110 may transmit different signals to each of the STAs 131-134substantially simultaneously, using SDMA techniques. Similarly, each STA131-134 may transmit different signals to the AP 110 substantiallysimultaneously, and the AP 110 may separate the combined receivedsignals into the individual signals from each STA using SDMA techniques.Non-immediate block acknowledgments may be used to avoid potentialtimeouts that could occur if each STA expected to receive anacknowledgment to its transmission within a predefined timeout periodthat started immediately after the conclusion of that transmission.

Although AP 110 is shown with four antennas 120 to communicatewirelessly with up to four STAs at a time using SDMA techniques, otherembodiments may have other arrangements (e.g., AP 110 may have two,three, or more than four antennas). Each STA may have at least oneantenna to communicate wirelessly with the AP 110. In some embodimentsthe STA antenna(s) may be adapted to operate omnidirectionally, but inother embodiments the STA antenna(s) may be adapted to operatedirectionally. In some embodiments the STAs may be in fixed locations,but in other embodiments at least some of the STAs may be moving duringand/or between communications sequences. In some embodiments the AP maybe in a fixed location, but in other embodiments the AP may be movingduring and/or between communications sequences.

FIG. 2 shows a timing diagram of a communications sequence usingnon-immediate block acknowledgments, according to an embodiment of theinvention. In FIG. 2, transmissions from a base station are on the lineindicated as AP, while transmissions from two mobile devices are on thelines indicated as STA1 and STA2, respectively. The AP line is furthersub-divided into spatial channels, labeled as STA 1 (directionaltransmissions from the base station to the mobile device STA1), STA 2(directional transmissions from the base station to the mobile deviceSTA2). Only two STAs are shown in FIG. 2, however, other embodiments mayinclude any feasible number of STAs operating at the same time andfollowing the sequence shown. FIG. 2 assumes that the AP is alreadyenabled to communicate with multiple STAs at the same time using SDMAtechniques, and any process that might have been used to create suchenablement is not shown. FIG. 2 shows a data phase followed by anacknowledgment phase. During the data phase the AP may poll the STAs fordata during the poll period, and the polled STAs may respond with databursts to the AP during the response period, a data burst comprising oneor more blocks of data transmitted in sucesssion. During theacknowledgment phase the AP may send a separate acknowledgment to eachSTA from which data was correctly received. The AP may withhold anacknowledgment to any STA from which data was not correctly received.Any one or more of the data phase, acknowledgment phase, poll period,and response period may have predetermined durations that are known bythe AP and/or STAs. In some embodiments the length of the data phaseand/or response period may be specified in the poll.

As shown in FIG. 2, the relevant STA's (those in the same poll group)may each be polled at the same time during the poll period using adefined poll format. In some embodiments, the polls to the STAs may betransmitted substantially simultaneously using the directionalcapabilities of SDMA transmissions, but other embodiments may use othertechniques.

During the response period, each STA that received a poll may respond bysending a data burst to the AP. In some embodiments, each data burst mayconsist of multiple sub-bursts, with each sub-burst conforming to theformat of a medium access control protocol data unit (MPDU), althoughthe scope of the invention is not limited in this respect. Because theSDMA format may not allow the AP to transmit and receive simultaneously,the AP may not transmit any acknowledgments to the data burst or any ofthe sub-bursts during the response period when the AP is receiving. Thusany acknowledgment of the data burst or any sub-bursts may wait untilthe acknowledgment phase, when a single acknowledgment to a given STAmay be used to acknowledge the data burst from that STA. One of thesub-bursts, (e.g., the final MPDU, although the scope of the inventionis not limited in this manner) may specify whether any acknowledgment isrequested, and if so, what type of acknowledgment.

In some embodiments, a non-immediate block acknowledgment may berequested. A block acknowledgment may acknowledge multiple sub-burstswith a single acknowledgment. A non-immediate acknowledgment mayindicate that the AP will wait until after the data phase before sendingthe acknowledgment, even if the STA completed its transmission wellbefore the end of the data phase. The non-immediate block acknowledgmentrequest therefore may be a request for a single acknowledgment for theentire data burst, with the acknowledgment expected to be received atsome time after the end of the data phase. In some embodiments the‘non-immediate’ element may be specified in the acknowledgment request,but in other embodiments may be a required element with being specifiedin the acknowledgment request. In some embodiments, each STA may start atimeout period after the end of the data phase. If the expectedacknowledgment is received before the end of that timeout, the STA mayassume that the data burst was correctly received by the AP. If theexpected acknowledgment is not received before the end of that timeout,the STA may assume that the data burst was not correctly received by theAP, and may take appropriate corrective action. In some embodiments, thecorrective action may include retransmitting the data burst to the AP inresponse to a subsequent poll.

FIG. 3 shows a flow chart of a method of operation of a base station,according to an embodiment of the invention. The base station maytransmit to, and/or receive from, multiple STAs substantiallysimultaneously by using SDMA techniques, but for simplicity only thecommunications between one STA and the base station are described in theflow chart. In flow chart 300, the base station may transmit a poll to aSTA at 310, requesting that the STA respond by sending a data burst. Thedata burst transmitted by the STA in response to the poll may bereceived at 320. At 330, the data burst may be examined for the presenceof a request for a non-immediate (specified or inherently required)block acknowledgment. If no such request is found, or if a differenttype of acknowledgment is requested, control may exit at 340 to otherprocessing not shown. If a non-immediate block acknowledgment isdetected, there may be a delay at 350 until the data phase ends and theacknowledgment phase starts. The end of the data phase and/or the startof the acknowledgment phase may be determined in various ways, such as ahardware timer.

In some embodiments, the protocol being used may default to anon-immediate block acknowledgment format without the use of anacknowledgment request in the data burst, so that decision block 330automatically defaults to ‘yes’. During the acknowledgment period, ablock acknowledgment may be transmitted to the relevant STA at 360.

FIG. 4 shows a flow chart of a method of operation of a mobile device,according to an embodiment of the invention. In flow chart 400, at 410the mobile device may receive a poll from a base station, triggering themobile device to respond by transmitting a data burst at 420. In someembodiments the data burst may include a request for a non-immediateblock acknowledgment, while in other embodiments, the protocol beingused may default to a non-immediate block acknowledgment format withoutthe use of such a request in the data burst. After completion of thedata burst, the STA may wait at 430 until the end of the data period.

After the end of the data period, the STA may begin an acknowledgmenttimeout period at 440. In some embodiments the timeout period may bemeasured by a hardware timer, but other embodiments may use othertechniques. If a block acknowledgment is received from the base stationbefore the end of the timeout period as determined by the loop at 450and 470, the timeout period may be cancelled and this processing exitsat 460. However, if the block acknowledgment has not been received bythe end of the timeout period, as determined by the loop at 450 and 470,control may move to some form of error processing at 480. Such errorprocessing may include retransmitting the data burst after receiving asubsequent poll from the base station. In some embodiments blocks440-480 may be applied to individual sub-bursts rather than to the databurst as a whole

The operations described above may include processes needed to cause acomputer platform to perform the operations, such as but not limited toplacing data into at least one transmit queue and/or reading data fromat least one receive queue.

Embodiments of the invention may be implemented in one or a combinationof hardware, firmware, and software. Embodiments of the invention mayalso be implemented as instructions stored on a machine-readable medium,which may be read and executed by a computing platform to perform theoperations described herein. A machine-readable medium may include anymechanism for storing or transmitting information in a form readable bya machine (e.g., a computer). For example, a machine-readable medium mayinclude read only memory (ROM); random access memory (RAM); magneticdisk storage media; optical storage media; flash memory devices;electrical, optical, acoustical or other form of propagated signals(e.g., carrier waves, infrared signals, digital signals, etc.), andothers.

FIG. 5 shows a block diagram of a base station, according to anembodiment of the invention. Computing platform 550, which may performprocessing suitable for a base station, may include one or moreprocessors, and in some embodiments at least one of the one or moreprocessors may be a digital signal processor (DSP). In the illustratedembodiment, AP 110 has four antennas 120, but other embodiments may havetwo, three, or more than four antennas. For each antenna, base station110 may have a modulator/demodulator 520, an analog-to-digital converter(ADC) 530, and a digital-to-analog converter (DAC) 540. The combinationof demodulator-ADC may convert received radio frequency signals from theantenna into digital signals suitable for processing by the computingplatform 550. Similarly, the combination of DAC-modulator may convertdigital signals from the computing platform 550 into radio frequencysignals suitable for transmission through the antenna. Other componentsnot shown may be included in the illustrated blocks as needed, such asbut not limited to amplifiers, filters, oscillators, multiple quantitiesof ADCs and/or DACs where only one is shown, etc.

FIG. 6 shows a block diagram of a mobile device, according to anembodiment of the invention. The illustrated components of mobile device131 may include a computing platform 650, antenna 621,modulator/demodulator 620, ADC 630, and DAC 640 that may be functionallysimilar to those similarly-named components of FIG. 5, but the device ofFIG. 6 is shown with a single antenna/modulator/demodulator/ ADC/ DACcombination, and the computing platform 650 may perform the operationspreviously described for a mobile device rather than a base station,although various embodiments of the invention are not limited in theserespects.

FIG. 7 shows some communications formats that may be used in particularembodiments of the invention, although other embodiments are not limitedin this respect. Various embodiments may include some, all, or none ofthe illustrated elements of FIG. 7, and the order the elements may bedifferent from that shown. Headers, trailers, and other elements neededto establish the start and end of a communications block are not shown.In the embodiment of FIG. 7:

1) All: Each transmission in the communications sequence may contain theaddress of the transmitting device and the address of the intendedrecipient. Because other APs and STAs may be within range, includingthese addresses may prevent confusion within the network.

2) Poll from AP: In addition to the aforementioned addresses, the pollmay comprise a Response Type Flag indicating the type of response thatis requested from the STAs (e.g., the STAs will wait until a predefinedresponse period before responding, the response period beginning apre-defined time period after the end of the poll). The poll may alsocomprise a Response Period Length (e.g., the response period lasts forthe indicated length of time, and the STA must complete its responsewithin that time period). Finally, the block may end with a validitycheck character to assure the block was received correctly (e.g., acyclic redundancy check (CRC) character).

3) Sub-burst from STA: During the response period, the STA may respondwith a data burst containing a series of multiple sub-bursts. Inaddition to the aforementioned addresses, each sub-burst may contain anidentifier that uniquely identifies this particular sub-burst within thedata burst (e.g., an MPDU ID number). After the data portion, the blockmay contain an acknowledgment request flag that indicates whether anacknowledgment is expected, and if so, what type of acknowledgment. Forall but the last sub-burst, a ‘no acknowledgment’ flag may be used,indicating no acknowledgment is requested for these individualsub-bursts. For the last sub-burst, a block acknowledgment request maybe indicated, indicating that a block acknowledgment is expected for thedata burst as a whole. The request may specify a non-immediate blockacknowledgment (i.e., an acknowledgment timeout period does notautomatically begin immediately after the sub-burst containing therequest). Alternatively, the non-immediate element may be an understoodrequirement that is built into the block acknowledgment format, so thatthe block acknowledgment is not expected until after the response periodis over even though the request does not specify ‘non-immediate’.

4) Acknowledgment from AP: In addition to the aforementioned addresses,the block acknowledgment from the AP may contain an acknowledgment bitmap, with a separate bit in the bit map associated with each sub-burst.Each bit in the bit map may be asserted (e.g., a logic ‘1’) if theassociated sub-burst was correctly received by the AP, or may bede-asserted (e.g., a logic ‘0’) if the associated sub-burst was notcorrectly received by the AP. Incorrect receipt may include, but is notlimited to, such things as: a) the associated sub-burst was notreceived, b) the associated sub-burst failed a CRC check, c) theassociated sub-burst had an incorrect format or was of an incorrecttype, d) etc. In one embodiment the bit map contains a pre-definednumber of bits to accommodate the maximum allowed number of sub-bursts,but other embodiments may use other arrangements (e.g., the bit map maycontain only as many bits as the data burst contained sub-bursts, thebit map may be sized and organized according to how the sub-bursts areidentified, etc.). Finally, the acknowledgment block may contain a CRCcharacter so that the STA may verify the acknowledgment block wascorrectly received.

The foregoing description is intended to be illustrative and notlimiting. Variations may occur to those of skill in the art. Thosevariations are intended to be included in the various embodiments of theinvention, which are limited only by the spirit and scope of theappended claims.

1. An apparatus, comprising a first electronic device adapted to:transmit a data burst during a data phase in response to a poll from asecond electronic device; begin a timeout period after an end of thedata phase; and receive a block acknowledgment from the secondelectronic device during the timeout period.
 2. The apparatus of claim1, wherein the data burst comprises a block acknowledgment request. 3.The apparatus of claim 2, wherein the block acknowledgment requestcomprises a non-immediate block acknowledgment request.
 4. The apparatusof claim 1, wherein the first electronic device is further adapted tobegin the timeout period after a length of time indicated in the poll.5. The apparatus of claim 1, wherein the first electronic device isfurther adapted to: transmit multiple sub-bursts within the data burst;and receive individual acknowledgments to individual ones of thesub-bursts within the block acknowledgment.
 6. The apparatus of claim 1,wherein the apparatus comprises: a computing platform; and amodulator/demodulator coupled to the computing platform.
 7. Theapparatus of claim 6, wherein the apparatus further comprises an antennacoupled to the modulator/demodulator.
 8. The apparatus of claim 1,wherein the first electronic device comprises a mobile device.
 9. Theapparatus of claim 1, wherein the second electronic device comprises abase station.
 10. An apparatus, comprising a first electronic deviceadapted to: transmit polls to multiple second electronic devicessubstantially simultaneously on a same frequency using spatial divisionmultiple access techniques; receive a data burst from a particular oneof the multiple second electronic devices during a data phase subsequentto said transmitting the polls, substantially simultaneously withreceiving other data bursts from others of the multiple secondelectronic devices; and transmit a block acknowledgment to theparticular second electronic device after the data phase using spatialdivision multiple access techniques.
 11. The apparatus of claim 10,wherein the first electronic device is further adapted to receive ablock acknowledgment request within the data burst.
 12. The apparatus ofclaim 10, wherein the first electronic device is further adapted totransmit an indicator of a length of the data phase within at least oneof the polls.
 13. The apparatus of claim 10, wherein the firstelectronic device is further adapted to: receive multiple sub-burstswithin the data burst from the particular one of the multiple secondelectronic devices; and transmit individual acknowledgments within theblock acknowledgment for individual ones of the sub-bursts.
 14. Theapparatus of claim 10, wherein the first electronic device comprises: acomputing platform; and at least four modulator/demodulators coupled tothe computing platform.
 15. The apparatus of claim 14, wherein the firstelectronic device further comprises at least four antennas, each antennacoupled to at least one of the modulator/demodulators.
 16. A method,comprising: transmitting a first poll to a first electronic device and asecond poll to a second electronic device substantially simultaneouslyon a same frequency using spatial division multiple access techniques;receiving a first data burst from the first electronic device and asecond data burst from the second electronic device substantiallysimultaneously on the same frequency subsequent to said transmitting;detecting a non-immediate block acknowledgment request in at least oneof the first and second data bursts; and transmitting a first blockacknowledgment to the first electronic device and a second blockacknowledgment to the second electronic device substantiallysimultaneously on the same frequency using spatial division multipleaccess techniques, subsequent to said receiving.
 17. The method of claim16, wherein said receiving the first data burst comprises receivingmultiple sub-bursts within the first data burst.
 18. The method of claim17, wherein said transmitting comprises transmitting individualacknowledgments for individual ones of the multiple sub-bursts.
 19. Amethod, comprising: transmitting a data burst in response to a poll froma base station, the data burst comprising a block acknowledgmentrequest; and receiving a block acknowledgment subsequent to the dataphase.
 20. The method of claim 19, wherein: said transmitting comprisestransmitting multiple sub-bursts within the data burst; and saidreceiving comprises receiving individual acknowledgment indicators forindividual ones of the multiple sub-bursts.
 21. A machine-readablemedium that provides instructions, which when executed by a computingplatform, cause said processing platform to perform operationscomprising: placing into a transmit queue a response to a poll, theresponse comprising a data burst including multiple sub-bursts;detecting an end to a data phase; and reading from a receive queue ablock acknowledgment in response to said transmitting, subsequent tosaid detecting.
 22. The medium of claim 21, wherein the operation ofplacing comprises placing into the transmit queue a medium accesscontrol protocol data unit containing the block request.
 23. The mediumof claim 21, wherein the operation of placing comprises: placing into afinal one of the multiple sub-bursts a block acknowledgment request; andplacing into others of the multiple sub-bursts a no-acknowledgmentrequest.
 24. A machine-readable medium that provides instructions, whichwhen executed by a computing platform, cause said processing platform toperform operations comprising: placing into at least one transmit queuepolls to multiple electronic devices; receiving data from the multipleelectronic devices in at least one receive queue; detecting a blockacknowledgment request in the received data from at least one of themultiple electronic devices; waiting until a predefined time period isended; and placing into the at least one transmit queue a blockacknowledgment to the at least one of the multiple electronic devices.25. The medium of claim 24, wherein the operation of receiving dataincludes receiving data from multiple medium access control protocoldata units.
 26. The medium of claim 24, wherein the operation of placinga block acknowledgment comprises placing multiple indicators in theblock acknowledgment to acknowledge multiple correctly received portionsof the received data.
 27. The medium of claim 24, wherein the operationsfurther comprise using spatial division multiple access techniques totransmit the block acknowledgment.